Abstract: An oscillator usable for a TDMA type wireless mobile communication device in which an average current at the communication terminal is decreased. The oscillator has a switching circuit or a timing circuit which controls an operating current of an amplifying element 8 for oscillation and reduces an average current in a TDMA operation without changing a voltage applied to a passive element constituting the oscillator. In particular, before initiating oscillation, elements in a negative impedance circuit are charged with a current of a value which does not cause the oscillation of the oscillator, and at the time of initiating the oscillation, a current capable of oscillating the oscillator is supplied to the negative impedance circuit.

Abstract: A radio relay system including a water-proof conductor housing on which is located a pair of antennas, one antenna being used for transmitting and receiving radio carrier wave signals of a first and a second frequency, respectively, while the other antenna is used for transmitting and receiving radio carrier wave signals of a third and a fourth frequency, respectively. A skirt for each of the antennas is located adjacent the antennas on the housing, one skirt has a length equal to a quarter of the wavelength of the first frequency while the other skirt has a length equal to a quarter wavelength of the third frequency.

Abstract: A radio relay system which comprising an external conductor, a first antenna installed on the externals conductor for transmitting and receiving a first radio carrier wave, a second antenna installed on the external conductor for transmitting and receiving a second radio carrier wave, a skirt provided around the second antenna, the skirt having a length equal to a quarter of the wavelength of the second radio carrier signal, and a relay device which includes a branching filter for extracting a part of the second radio carrier wave as a carrier wave, an adjusting unit for adjusting the amplitude and phase of the carrier wave extracted by the branching filter, and a combining unit for combining the carrier wave extracted by the branching filter with the second radio carrier wave received through the first antenna, and the relay device transmitting as the second radio carrier through the second antenna the first radio carrier wave received through the first antenna.

Abstract: A base station for a mobile communications system including an antenna for transmitting a radio carrier wave to a mobile communications device and receiving signals therefrom, a coaxial external conductor including a skirt in the form of a sun shade having a length equal to a quarter wavelength of the radio carrier wave, a radio section located inside the coaxial external conductor for providing radio communication with the mobile communication device via the antenna, and a connecting section connecting the radio section to a telephone line and where the antenna is configured in the form of an upper disk of a discone antenna and where the skirt is a lower conical member of the discone antenna.

Abstract: A power amplifier comprises a power amplifying element for driving a load wherein a forward bias voltage applied between an input terminal and an output terminal of said power amplifying element which varies depending upon an output current of said power amplifying element, is detected and converted into a calibration current to feed back the current to the input terminal of said power amplifying element to calibrate variation of the forward bias voltage of said power amplifying element in linear variation in full cycle of input signal given by a signal source and to prevent cut-off of said power amplifying element in full cycle.